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Gravity is real you dumb fuckers

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A really interesting idea was that the universe in fact had a very complex spacetime geometry (i.e. not a sphere) and in fact what we perceive as inhomogeneity in the microwave background is actually the curves and loops of the universe (and that we are in fact basically looking back at ourselves).

I have a question. Is there a possibility of the universe collapsing on itself? Have we thought anything about that? Einstein wasn't even sure whether the universe was infinite IIRC.

The universe is finite without boundaries as far as we can tell. In other words, it's the surface of a sphere. Is it collapsing on itself? Well, the theory is that the end of the universe would either end in a heat death or by collapsing back on itself. If mass pressure is high enough that it eventually slows and then reverses the rate of expansion of the universe, then it collapses on itself. For a long time, it was assumed the latter would occur, but now evidence seems to be suggesting that the expansion of the universe is accelerating, which means it will not collapse on itself.

Top of this page dude. They didn't detect shit. They only observed gravitational lensing, with no massive object appearing responsible for it. There has yet to be any direct observation of dark matter. All they detected was gravity, and they can't explain why it is there, so they are saying "dark matter must be doing it!"

What do you mean by "direct observation"? Dark matter by definition can only be detected due to its gravitational effect. If we could see it then it wouldn't be dark matter.

That's getting into "God exists because by definition He exists" territory. All we detected was gravity. We don't know for certain that something has to "cause" gravity.

I have a question. Is there a possibility of the universe collapsing on itself? Have we thought anything about that? Einstein wasn't even sure whether the universe was infinite IIRC.

The universe is finite without boundaries as far as we can tell. In other words, it's the surface of a sphere. Is it collapsing on itself? Well, the theory is that the end of the universe would either end in a heat death or by collapsing back on itself. If mass pressure is high enough that it eventually slows and then reverses the rate of expansion of the universe, then it collapses on itself. For a long time, it was assumed the latter would occur, but now evidence seems to be suggesting that the expansion of the universe is accelerating, which means it will not collapse on itself.

Top of this page dude. They didn't detect shit. They only observed gravitational lensing, with no massive object appearing responsible for it. There has yet to be any direct observation of dark matter. All they detected was gravity, and they can't explain why it is there, so they are saying "dark matter must be doing it!"

What do you mean by "direct observation"? Dark matter by definition can only be detected due to its gravitational effect. If we could see it then it wouldn't be dark matter.

That's getting into "God exists because by definition He exists" territory. All we detected was gravity. We don't know for certain that something has to "cause" gravity.

Well... something has to be responsible for it. Dark matter (which apparently is the mainstream accepted idea right now) or some other thing.

Top of this page dude. They didn't detect shit. They only observed gravitational lensing, with no massive object appearing responsible for it. There has yet to be any direct observation of dark matter. All they detected was gravity, and they can't explain why it is there, so they are saying "dark matter must be doing it!"

What do you mean by "direct observation"? Dark matter by definition can only be detected due to its gravitational effect. If we could see it then it wouldn't be dark matter.

That's getting into "God exists because by definition He exists" territory. All we detected was gravity. We don't know for certain that something has to "cause" gravity.

Well... something has to be responsible for it. Dark matter (which apparently is the mainstream accepted idea right now) or some other thing.

I am saying that it is silly to assume gravity must be caused by something. Considering how little we actually know about gravity.

Top of this page dude. They didn't detect shit. They only observed gravitational lensing, with no massive object appearing responsible for it. There has yet to be any direct observation of dark matter. All they detected was gravity, and they can't explain why it is there, so they are saying "dark matter must be doing it!"

What do you mean by "direct observation"? Dark matter by definition can only be detected due to its gravitational effect. If we could see it then it wouldn't be dark matter.

That's getting into "God exists because by definition He exists" territory. All we detected was gravity. We don't know for certain that something has to "cause" gravity.

Well... something has to be responsible for it. Dark matter (which apparently is the mainstream accepted idea right now) or some other thing.

Sure.

I mean, assuming that God was detectable by a certain phenomenon, and the only definition of God was that it was the source of that phenomenon...

Yeah, this is just like the time from the 1886 - 1930 that astronomers tried to fix their theory of gravity and the like when they discovered that Uranus' orbit was not what was predicted by the model - it just didn't match the calculations. Instead of looking for the correct model they tried to find ways for their model to be correct.

Bastards. It's almost like they don't know how to do science.

Just seems a little stupid to me to close out the possibility that x model is fundamentally broken. "There MUST be dark matter because otherwise our model doesn't work!" They must realize that the universe does not operate according to their model.

Generally, if a model doesn't match the observable data, you try to modify it so that it does. This is the sensible thing to do.

you can apply fractions and a natural log to any set of completely random data and turn that bad boy into a straight line and then write a thesis proving ridiculous shit like cloud altitude and its effects on your headshot percentages in team fortress

There are several ways where mass just doesn't add up in the universe. Anywhere from Big Bang Models, to the observed rotational speed of galaxies, to lensing effects, to collision models, to the speed of galaxies being greater then their escape velocity out of clusters, yet them never escaping. Of course these are all gravity effects, because the whole point about dark matter is that gravity does not behave as we would expect. The notion "how little we actually know about gravity" seems stupid though. Our leading theory of gravity (Relativity) is 90 years old, never disproven, or proven wrong, and keeps on getting more supported proof, like very recently with the twin quasars proving time altering effects to within 99.97% as predicted (the 0.03 is due to insensitivity in measurement mostly, they can't guarantee more accurate). Note that our theory of gravity is also extremely elegant. The whole theory is derived from a thought experiment, which if taken to it's full conclusion leads to a bunch of very strange conclusions, and all of those strange conclusions, so far, have proven true.

The fact that we are not able to incorperate quantum mechanics and general relativity into one seemless theory does not mean that one of them is incorrect. Both of them are as succesful as a scientific theory can be: 100% accurate prediction rate for any observed phenomenon they deal with. The fact that they don't mesh is painful and awkward, but hardly a reason to throw either of them out of the window. Quantum Mechanics is also way "weirder" and counterintuitive then Relativity, or even Dark Matter, in my opinion. Who says that QM isn't wrong then, if we absolutely can only have one? (Which i wouldn't say at all).

Generally, if a model doesn't match the observable data, you try to modify it so that it does. This is the sensible thing to do.

you can apply fractions and a natural log to any set of completely random data and turn that bad boy into a straight line and then write a thesis proving ridiculous shit like cloud altitude and its effects on your headshot percentages in team fortress

Relevance being?[/QUOTE]

no real relevance. The talk about models and fitting reminded me of all my 400394209348 physics labs from college where we did such things that I thought was funny

Yeah, this is just like the time from the 1886 - 1930 that astronomers tried to fix their theory of gravity and the like when they discovered that Uranus' orbit was not what was predicted by the model - it just didn't match the calculations. Instead of looking for the correct model they tried to find ways for their model to be correct.

Bastards. It's almost like they don't know how to do science.

Just seems a little stupid to me to close out the possibility that x model is fundamentally broken. "There MUST be dark matter because otherwise our model doesn't work!" They must realize that the universe does not operate according to their model.

You're exaggerating the rigidity of the community's attachment to dark matter/energy patches. They're being investigated as possibilities; they are not the only possibilities being investigated. There may come a time when relativity and quantum theory have to be discarded Newton-style, but we're not at that point yet.

Top of this page dude. They didn't detect shit. They only observed gravitational lensing, with no massive object appearing responsible for it. There has yet to be any direct observation of dark matter. All they detected was gravity, and they can't explain why it is there, so they are saying "dark matter must be doing it!"

What do you mean by "direct observation"? Dark matter by definition can only be detected due to its gravitational effect. If we could see it then it wouldn't be dark matter.

That's getting into "God exists because by definition He exists" territory. All we detected was gravity. We don't know for certain that something has to "cause" gravity.

Well... something has to be responsible for it. Dark matter (which apparently is the mainstream accepted idea right now) or some other thing.

I am saying that it is silly to assume gravity must be caused by something. Considering how little we actually know about gravity.

Uh, and what are you basing this on? From observation and theory, we know that gravity is "caused by" mass (that is, a massive body will exert a gravitational pull on other bodies). So far as we know, gravity, nor any other force is caused by "nothing", which would seem to imply that it occurs randomly or unpredictably. Gravity is (partly) predictable, and indeed, the entire basis of science is that the universe is a predictable place (which has so far turned out to be true, because science is so successful).

So, yeah, its pretty damn safe to say that gravity is caused by something. If it isn't then we wont really know anyway.

So is there any thought on where dark matter actually hides? Presumably the effects are too small to really be measurable on macroscopic objects, and as Kakos was saying, we've only "directly" interacted with neutrinos. Yet, hypothetically, most of the matter in the universe is dark.

So where is it? From what I can tell, it looks like it's somehow "attached" to regular matter. The observations of those two galaxies made it seem as if the dark matter existed more or less within the confines of the observable matter, as if the latter was swimming in a soup comprised of the former. Is it assumed, then, that dark matter exists as a semi-uniform blob that hangs out across the entirety of galaxies? Would, for example, our solar system be steeped in a big ol' sea of dark matter? If that's the case, could that account for our inability to really see its effects from here on Earth? If we were surrounded by a uniform soup of dark matter, much of its effect would pretty much cancel out.

ElJeffe on January 2008

Maddie: "I named my feet. The left one is flip and the right one is flop. Oh, and also I named my flip-flops."

The main dark matter candidate at the moment is the neutralino, a particle that is predicted in some string theory / supersymmetry theory. A neutrino with a spin 1/2 off of that of known neutrino's, it's predicted to have a high mass, and only interacts through gravity, and possibly the weak atomic force. Note no supersymmetry theory is currently proven (although the LHC should shed some light on this, some particles predicted by supersymmetry are supposed to be created at the collision energies of the LHC). There are currently several projects underway to detect neutralino's. (Much in the same way as detecting neutrino's, by huge reservoirs of extremely undisturbed liquids, deep below mountains and such, hoping to catch one colliding with an atom exactly head on, and detecting the energy from this).

So is there any thought on where dark matter actually hides? Presumably the effects are too small to really be measurable on macroscopic objects, and as Kakos was saying, we've only "directly" interacted with neutrinos. Yet, hypothetically, most of the matter in the universe is dark.

So where is it? From what I can tell, it looks like it's somehow "attached" to regular matter. The observations of those two galaxies made it seem as if the dark matter existed more or less within the confines of the observable matter, as if the latter was swimming in a soup comprised of the former. Is it assumed, then, that dark matter exists as a semi-uniform blob that hangs out across the entirety of galaxies? Would, for example, our solar system be steeped in a big ol' sea of dark matter? If that's the case, could that account for our inability to really see its effects from here on Earth? If we were surrounded by a uniform soup of dark matter, much of its effect would pretty much cancel out.

I think that's how it's supposed to work. It wouldn't necessarily be a 'uniform blob', since it would have to orbit the center of the galaxy like everything else.

I know this is way late, but there is a "disorder" where a person associates a smell with a color, so whenever they see that color they smell whatever they associate it with. Therefore, people do smell colors.

I know this is way late, but there is a "disorder" where a person associates a smell with a color, so whenever they see that color they smell whatever they associate it with. Therefore, people do smell colors.

I know this is way late, but there is a "disorder" where a person associates a smell with a color, so whenever they see that color they smell whatever they associate it with. Therefore, people do smell colors.

I was being a smartass, but yeah, it happens with all sorts of sensations. It's called synesthesia. Some people claim to see music, and those people are generally musically gifted. It's usually not such a blessing, instead a weirdo fucking curse.

I know this is way late, but there is a "disorder" where a person associates a smell with a color, so whenever they see that color they smell whatever they associate it with. Therefore, people do smell colors.

I was being a smartass, but yeah, it happens with all sorts of sensations. It's called synesthesia. Some people claim to see music, and those people are generally musically gifted. It's usually not such a blessing, instead a weirdo fucking curse.

I know someone who tastes a sweet taste when she hears a major chord, bitter for minor, and its crazy. She is an amazing musician.

There are rare instances of people having that gift with mathematics as well.

Anyway, physics is at that point where mathematical and theoretical inference is driving experiment rather than the other way around, which is weird for science and makes everyone uncomfortable. But as I recall, black holes were predicted by the math of general relativity decades before we actually discovered one, and likewise with the neutrino.

Its a very interesting situation in physics today. Everyone is searching for the one all-encompassing theory to explain all physics at every scale. Yet, whenever we delve deeper, whenever we find smaller particles, their physics contradict everything we thought we had learned.

My feeling is that this can go on infinitely, that there are an infinite number of sets of rules; one for every magnitude, of which there is no limit.

Like most experiments it is not conclusive proof in and of itself; modified theories of gravity could still explain the observations presented in that paper. However, it seems odd that the modified theories of gravity would behave exactly like clusters of mass hanging around in galaxies. This is much like saying "epicycles could explain the retrograde motion of the planets, but it seems odd that the planets behave exactly like we are all in elliptical orbits around the sun".

Also, in response to salvation122's post:

Physicists do admit that the model is incredibly fucking broken because shit is expanding way too fast. The model is broken in other ways too! But the whole point of physics is that you look at how your model is broken and you say "what could explain this?" You seem to have this picture of scientists desperately throwing ridiculous shit in to save their explanation of the universe. That's not what's happening- scientists are trying hard to come up with something, anything, to explain what they see. In this case the "tons of conveniently invisible matter in just the right spot" theory really does explain the observations better than anything else we've come up with.

I've done a good amount of research on them, and it's pretty much the prime example of something we absolutely can't explain. Physics as we know it on Earth does not apply to Black Holes, they defy pretty much everything we know to be true here.

Top of this page dude. They didn't detect shit. They only observed gravitational lensing, with no massive object appearing responsible for it. There has yet to be any direct observation of dark matter. All they detected was gravity, and they can't explain why it is there, so they are saying "dark matter must be doing it!"

What do you mean by "direct observation"? Dark matter by definition can only be detected due to its gravitational effect. If we could see it then it wouldn't be dark matter.

That's getting into "God exists because by definition He exists" territory. All we detected was gravity. We don't know for certain that something has to "cause" gravity.

Well... something has to be responsible for it. Dark matter (which apparently is the mainstream accepted idea right now) or some other thing.

I am saying that it is silly to assume gravity must be caused by something. Considering how little we actually know about gravity.

Uh, and what are you basing this on? From observation and theory, we know that gravity is "caused by" mass (that is, a massive body will exert a gravitational pull on other bodies). So far as we know, gravity, nor any other force is caused by "nothing", which would seem to imply that it occurs randomly or unpredictably. Gravity is (partly) predictable, and indeed, the entire basis of science is that the universe is a predictable place (which has so far turned out to be true, because science is so successful).

So, yeah, its pretty damn safe to say that gravity is caused by something. If it isn't then we wont really know anyway.

I don't see how you can base gravity among the universe based on your understanding of gravity on earth. How do we know science was correct about the universe? We've been on the Moon and Earth, that's it. I just don't think it's fair to assume the ENTIRE rest of the universe is predictable in those ways. There's no way to know.

Top of this page dude. They didn't detect shit. They only observed gravitational lensing, with no massive object appearing responsible for it. There has yet to be any direct observation of dark matter. All they detected was gravity, and they can't explain why it is there, so they are saying "dark matter must be doing it!"

What do you mean by "direct observation"? Dark matter by definition can only be detected due to its gravitational effect. If we could see it then it wouldn't be dark matter.

That's getting into "God exists because by definition He exists" territory. All we detected was gravity. We don't know for certain that something has to "cause" gravity.

Well... something has to be responsible for it. Dark matter (which apparently is the mainstream accepted idea right now) or some other thing.

I am saying that it is silly to assume gravity must be caused by something. Considering how little we actually know about gravity.

Uh, and what are you basing this on? From observation and theory, we know that gravity is "caused by" mass (that is, a massive body will exert a gravitational pull on other bodies). So far as we know, gravity, nor any other force is caused by "nothing", which would seem to imply that it occurs randomly or unpredictably. Gravity is (partly) predictable, and indeed, the entire basis of science is that the universe is a predictable place (which has so far turned out to be true, because science is so successful).

So, yeah, its pretty damn safe to say that gravity is caused by something. If it isn't then we wont really know anyway.

I don't see how you can base gravity among the universe based on your understanding of gravity on earth. How do we know science was correct about the universe? We've been on the Moon and Earth, that's it. I just don't think it's fair to assume the ENTIRE rest of the universe is predictable in those ways. There's no way to know.

Er...we have telescopes. We can observe other parts of the universe. Do math and stuff.

Also it's a pretty fundamental question that gets asked all the time - are the laws of physics uniform?

I tend to find that to be an irrelevant question - if the laws change then surely something drives there to be a difference, so let's go find the sub theory.

Anyway, if they did, you would expect to be able to see where they did because the interaction of two separate rules governing interactions would require a transition region of some sort that would look different to both yet again.

I've done a good amount of research on them, and it's pretty much the prime example of something we absolutely can't explain. Physics as we know it on Earth does not apply to Black Holes, they defy pretty much everything we know to be true here.

I had always understood that the physical laws we use seem to break down, or at least change, under extreme conditions.

Seems like the unified field theory is a bit out of reach at the moment, judging by the hearty debate in this thread.

The more they look into the concept of a unifying theory to simply explain everything, the more they realize that it's going to be the most complicated nonsensical shit you can ever imagine. It will make you question who you are and where you belong.

Guys, I don't understand the idea of a physical law just breaking down. How would that even work?

It seems to me laws are just a human creation, labels we put on the phenomena of the universe, and if something fails to work as we expect, it is not because the law has broken down, but that ultimately our definition of the law was completely and utterly wrong. Truth?

I hope playing the Joker didn't have anything to do with this... I mean, I hope he wasn't driven to kill himself because of the role in some way. He was clearly taking the part pretty goddamned seriously.

So, yeah, its pretty damn safe to say that gravity is caused by something. If it isn't then we wont really know anyway.

I don't see how you can base gravity among the universe based on your understanding of gravity on earth. How do we know science was correct about the universe? We've been on the Moon and Earth, that's it. I just don't think it's fair to assume the ENTIRE rest of the universe is predictable in those ways. There's no way to know.

Dude, seriously? You're going to try and pull this shit?

Let's assume you've discovered something which is indeed profound (rather than simply a profound misunderstanding of science) with your statement that our limited experience with gravity (earth and the moon) means that "there's no way to know" about gravity in the universe at large.

We can state this as a more general principle - we cannot know the appropriateness of a general principle outside the domains and situations in which we arrived at this principle.

So, we can't know about gravity outside of the moon and earth.

Let's consider a far simpler principle which is also less controversial and better understood than gravity - "A metal expands when heated".

So, we've tested that all over Earth and the Moon, and we know why it happens thanks to electron microscopes and physical chemistry and the like. Now, what can we conclude about a metal expanding when heated under a different situation? What about on Mercury? Or Hades Gamma? Or Betegeuse IV? and so on and so forth. Under your maxim, we just cannot know. Which, were the ramifcations of your maxim to stop there would be somewhat workable (but a radically unorthodox view of the role of science).

The question is, how are we restricting domains? We have concepts such as "Earth" and "The Moon" but we certainly do not believe that the universe operates upon these macro-level and cognitive concepts - so, there's no rational reason to believe that the universe would differentiate its behaviour between domains such as "Earth" and "The Moon" and consequently no mechanism by which we can restrict your maxim in a similar fashion.

So, now we're dealing with arbitrarily precise positions - we've tested the expansion of metals in some particular position, and another particular position, and so on and so forth. But under your maxim we just cannot know whether metals will behave the same way under temperature in some other place which we haven't tested. So, even on the surface of the Earth, it turns out we can't really conclude anything interesting about metals, except for in areas in which we've already tested their behaviour.

But wait a minute - why are we assuming that the universe differentiates behaviour solely on position? What if time sensitivity is a factor? What if every 14th minute of every 1400th day metals will actually contract when heated? There's a whole range of time-related factors as well. So, it seems that we can't even predict how any given piece of metal will behave at any given time regardless of metal-related experiences we've had in the past, because we've only had experience with metals at particualr locations at particular times - who knows what will happen next week?

Then there are countless other variables which might be involved - temperatures used, atmospheric pressure, amount of light in the room, atmospheric composition, the shape of the metal, the size of the metal, the colour of the light in the room, the relative position of Jupiter, the abolute position of Jupiter, the quantum state of nearby cats and so on and so forth.

So, it seems like your maxim would render science impossible, and yet you're posting with the fruits of science's labour. Oops.

----

TL;DR

Science and rationality assumes the basic regularity of natural law. As science is by defnition a mechanism by which to make predictions about the future using limited datasets, this assumption is necessary for science and rationality to work*. As such, you can't seriously entertain your objection without invoking radical scepticism, which is bad.

* Which isn't to say that science cannot deal with irregularity, only that it must assume a basic state of uniformity.

Guys, I don't understand the idea of a physical law just breaking down. How would that even work?

I don't know how you'd describe it in terms of experience of what it would be like to physical laws break down around you.

What it does mean is that when you do the maths for the equations which describe the physical laws at extreme conditions the answers you get are crazy/impossible/incoherent or there are no solutions. For example, in some cases you end up dividing by zero, which tends not to make a lot of sense.

Guys, I don't understand the idea of a physical law just breaking down. How would that even work?

It seems to me laws are just a human creation, labels we put on the phenomena of the universe, and if something fails to work as we expect, it is not because the law has broken down, but that ultimately our definition of the law was completely and utterly wrong. Truth?

What does dividing by zero mean in math?

It's the same thing, sometimes exactly the same thing, that we talk about when we say the laws of physics "break down".

How do you even hope to understand or model something that happens before time exists?

I hope playing the Joker didn't have anything to do with this... I mean, I hope he wasn't driven to kill himself because of the role in some way. He was clearly taking the part pretty goddamned seriously.

But how do we distinguish between a true breakdown in the laws of physics and an upper limit in the human understanding of science?

Ah, the laws never break down even though sci-fi has somewhat abused that term and now it's undergoing extensive counseling.

By "break down" we mean that you get non-sense results within the model - i.e. X / infinity, X / 0 etc. It's essentially a term we use to say "this is the limit of this model, we need a more detailed thing to properly explain the phenomenon".

EDIT: A simpler explanation of physical laws breaking down would come from the various approximations used in solid state physics - superconductors for example at first glance appear to be a "break down" of the rules governing conductivity.